Reducing muzzle noise and flash from military and security personnel firearms (e.g., long guns and pistols) provide a significant tactical advantage in the field. Existing suppression technology reduces noise and flash, but comparatively little science exists to explain how current designs can be modified or replaced to provide enhanced suppressor performance, including the useful life span of the suppressor. Furthermore, even less design guidance exists that can lead to integration of suppressors into a firearm's barrel assembly. Lessons learned as a result of the ongoing military and homeland security based conflicts have indicated that increased use of current suppressors, as part of everyday operations, have led to shortened life cycles of suppressors, increased maintenance (and sometimes damage) of weapons, and considerable variability in weapon accuracy.
To set the stage for developing improved suppressors, it is necessary first to identify the critical elements of the attendant flow fields as thoroughly documented in Klingenberg, Firearmter and Heimerl, Joseph M., Firearm Muzzle Blast and Flash, AIAA Progress in Astronautics and Aeronautics, Volume 139, 1992.
These characteristics can be broken down into three core elements. The first two core elements are: the precursor blast; and a main blast set up by the expanding gases. The precursor blast consists of mostly air with a small amount of propellant and the main blast is made up of spherical pressure waves that quickly overtake the fired projectile. Both of these blasts are sources of low frequency noise that carry very far distances. The third core element is the highly visible gas flash which follows the blast.
In general, a gas flash occurs because air mixes with the fuel rich propellants and the high temperatures from the blast waves. The result of this mixture forms a gas flash which is greatly increased in the secondary flow region that occurs away from the muzzle of a firearm.
When a gas flash forms, it occurs in three parts: primary, intermediate, and secondary flashes. The primary flash forms at the muzzle in the supersonic flow region and is very small. An intermediate flash occurs directly behind the projectile, but in front of the Mach disk leading any supersonic flow region. (Not all firearms have supersonic discharge flows.) The secondary flash is the most severe, and it occurs downstream of the firearm muzzle, and after the normal shock resulting from the muzzle gas over-expansion. The large flash seen when firing a projectile is actually the secondary flash.
With an understanding of the three core elements involved in the blast and flash from a projectile, the individual components can be analyzed to assess their critical components. Considering the principal characteristics of the blast wave, Applicants have found that it is essentially a spherical blast wave that travels rapidly but also decays rapidly both strength-wise and time/distance-wise. Relative to the flow-field attendant to the flash, it establishes after or behind the main blast wave with a structure very similar to that of a traditional under-expanded jet plume often seen in propulsion applications. The key elements of the post-blast wave flow field are the free jet boundary and the highly under-expanded jet flow region all flowing strongly in the downstream axial direction. The over-expanded gas results in the normal shock or Mach disk, which causes the secondary flash and a significant portion of the noise. The important point is that the key physics of this type of flow structure is common in propulsion aerodynamics, and can be used to generate performance correlations for use in developing more efficient suppressor designs.
Within the firearms art, it is well known that a fired gun produces a sudden blast wave which is key to noise generation. That type of sudden blast wave is not present in a jet engine during flight.
There are a wide range of firearm suppressor designs. See, for example, the Prior Art shown in Applicants' FIGS. 1A-1D, All current designs apparently have three recurrent features: 1.) a circular or near circular cross-section with a diameter approximately five times the firearm's muzzle diameter; 2.) a solid outer surface so no gases can enter or escape the suppressor except through its entrance and exit ports; and 3.) complex flow nozzles, baffles and/or chambers interior to the suppressor for capturing the muzzle gases and mitigating the blast over-pressure level.
An alternate means of controlling supersonic flows, originally developed for propulsion applications, involves the use of flow mixer-ejectors, as discussed in U.S. Pat. No. 5,884,472 to Walter M Presz, Jr. and Gary Reynolds. Ejectors are well-known and documented fluid jet pumps that draw flow into a system and thereby increase the flow rate through that system. Mixer/ejectors are short compact versions of such jet pumps that are relatively insensitive to incoming flow conditions and have been used extensively in high-speed jet propulsion applications involving flow velocities near or above the speed of sound. See, for example, U.S. Pat. No. 5,761,900 to Walter M. Presz, Jr., which also uses a mixer downstream of a gas turbine nozzle to increase thrust while reducing noise from the discharge. Dr. Presz is a co-inventor in the present application. An ejector is a fluid dynamic pump with no moving parts.
Ejectors use viscous forces to lower the velocity and energy of a jet stream by ingesting lower energy flow which can lead to flow characteristics that may augment thrust, cool exhaust gases, suppress jet infrared signature, and importantly to ballistic applications, reduce attendant noise and flash. Mixers improve the performance characteristics of ejectors by inducing stirring, or axial vortices, that promote rapid mixing of the high velocity primary jet with the cooler, and sometimes heavier, ingested gas; thus resulting in more compact devices. Numerous patented products have derived from this concept. The mixer/ejector concept is well accepted within the aviation and jet propulsion community as an extremely efficient solution to aircraft noise and exhaust temperature suppression.
Gas turbine technology has yet to be applied successfully to firearm muzzle suppressors. If one were to replace an under-expanded jet engine exhaust for a ballistic blast from a firearm, in which hot gases are mixed and expelled with a projectile over the length of the barrel, it may be seen that such a technology could significantly reduce noise, flash, and provide outside air to the barrel that could be employed to cool and clean the suppressor components.
Accordingly, it is a primary objective of the present invention to provide a firearm suppressor that employs advanced fluid dynamic ejector pump principles to consistently deliver levels of noise and flash suppressor equal to or better than current suppressors.
It is another primary objective to provide an improved firearm suppressor with significantly increased useful life span over that of current firearm suppressors.
It is another primary objective to provide a self-cleaning, self-cooling firearm suppressor using mixer/ejector technology.
It is another primary objective to provide an improved firearm suppressor using mixer/ejector technology to control the muzzle blast wave and overexpansion flow for better suppression.
It is another object, commensurate with the above-listed objects, to provide an improved suppressor which is durable and safe to use.